In medicine, seemingly simple questions can often be surprisingly difficult to answer definitively.

Consider the relationship between breast cancer and exercise. While some studies have found that physical activity protects against the disease, others haven’t turned up any link at all. Now several new findings have begun to untangle these contradictions.

Results from a newly-published study by researchers at the German Cancer Research Center (the Deutsches Krebsforschungszentrum, or DKFZ) suggest that physical activity does lower breast cancer risk by as much as 30 percent. But the investigation, which compared 3,464 breast cancer patients with 6,657 healthy controls, also found that not all women benefit equally, and not all forms of breast cancer respond equally to exercise. Physical activity after age 50 appears to offer more powerful protection than exercise earlier in life, according to the results. The protective effects appeared up most clearly for hormone receptor positive forms of the disease. Other forms, including HER2, did not show the same strong association. Because weight gain, total energy intake, and BMI did not have any influence, researchers speculate that physical activity may protect by way of a hormonal mechanism.

There are still mysteries to untangle. In another study published this month, researchers at the National Cancer Institute in the U.S. found that active women had a 13 percent lower risk of the breast cancer than their sedentary counterparts. Women who were overweight or obese seemed to get more protection from exercise. So did those with a family history of breast cancer. But in this study, exercise seemed to protect more powerfully against estrogen receptor negative forms of the disease.

Despite the lingering puzzles, the sum of the evidence now strongly suggests that being physically active can lower the danger of breast cancer. And protecting yourself doesn’t require turning your life upside down. The German Cancer Research Center study found that even everyday activities–gardening, walking to the grocery store, pushing a lawnmower–offer protection. Said Karen Steindorf, MD, who headed up the analysis and is an associate professor at the DKFZ: “Our advice to all women is therefore to stay or become physically active also in the second half of your life.”

True, the aches and pains of middle age and beyond can make it hard to be active. But that’s also a time in life when health and longevity become all the more treasured. The latest findings should offer an additional nudge to get up and get moving. 

© 2009 PDQhealth 

Tags: breast cancer, exercise, physical activity